Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
Vol. 3 18-65
DEBUGGING AND PERFORMANCE MONITORING
MSR_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow the indicators
for general-purpose or fixed-function counters via a single WRMSR (see
Figure 18-24). Clear overflow indications when:
Setting up new values in the event select and/or UMASK field for counting or
sampling
Reloading counter values to continue sampling
Disabling event counting or sampling
18.15.3 At-Retirement Events
Many non-architectural performance events are impacted by the speculative nature
of out-of-order execution. A subset of non-architectural performance events on
processors based on Intel Core microarchitecture are enhanced with a tagging mech-
anism (similar to that found in Intel NetBurst microarchitecture) that exclude contri-
butions that arise from speculative execution. The at-retirement events available in
processors based on Intel Core microarchitecture does not require special MSR
programming control (see Section 18.18.7, “At-Retirement Counting”), but is limited
to IA32_PMC0. See Table 18-18 for a list of events available to processors based on
Intel Core microarchitecture.
Figure 18-24. Layout of MSR_PERF_GLOBAL_OVF_CTRL MSR
62
FIXED_CTR2 ClrOverflow
FIXED_CTR1 ClrOverflow
FIXED_CTR0 ClrOverflow
PMC1 ClrOverflow
2
1
0
PMC0 ClrOverflow
3132333435
Reserved
63
ClrCondChgd
ClrOvfBuffer